The present invention relates in general to a copying apparatus with a focus-adjusting mechanism and, more particularly, to an image copying machine for copying a paper image such as a document image, so as to print the image on paper.
For office workers dealing with increasing documentation, copying machines have been increasing their importance year by year. A total number of copying machines produced by various manufacturers is increasing. Along with this tendency, strict conditions for the manufacturing process of copying machines are imposed on the manufacturers so as to improve productivity while maintaining high quality standards.
In a conventional copying machine, an optical image obtained by light reflected by a paper document which is placed on a document scanning surface is incident on a lens through a first mirror. A document image from the lens is focused on a photoconductive drum through a second mirror. In order to clearly form the document image on the photoconductive drum with a high resolution and hence to improve the quality of the image to be copied, the optical system of the copying machine must be precisely controlled in accordance with the inherent focal length of the lens. When the copying machine of this type is manufactured in a factory, variations in optical characteristics (i.e., variations in focal length, etc.) of supposedly identical lenses, variations in component parts of the machine, and/or variations in the assembly process occur. As a result, during the manufacture of such copying machines, every optical system must be adjusted manually. The conventional adjustment process of such optical systems is cumbersome and time-consuming.